Polyketomethine dyes

ABSTRACT

Methine dyes with a polyketo group I ##STR1## where A is ##STR2## R 1  is a 5- or 6-membered cycloaliphatic radical which contains one or two hetero atoms from the group --NR 4  --, --O-- and --S-- and which may be fused to an isoaromatic or heteroaromatic group, R 2  and R 3  are identical or different C 1  -C 10  -alkyl groups or together one of the radicals R 1 , and m and n are identical or different integers from 0 to 3, are useful as drugs, for producing singlet oxygen, as sensitizers in electrophotographic layers and for photopolymerizations and as laser light sensitive dyes in optical recording media; also novel triketo- and tetraketomethine dyes.

The present invention relates to novel polyketonmethine dyes of thegeneral formula I ##STR3## where

A is a group of the formula A1 or A2 ##STR4##

R¹ is a 5- or 6-membered cycloaliphatic radical which contains one ortwo hetero atoms from the group --NR.sup. 4--, --O-- and --S-- and whichmay be fused to an isoaromatic or heteroaromatic group, where

R⁴ is a C₅ -C₇ -cycloalkyl group or a phenyl group which may carryhalogen, C₁ -C₄ -alkyl or -alkoxy as substituents, or a C₁ -C₂₀ -alkylgroup whose carbon chain may be interrupted by from one to five oxygenatoms in ether function and which may carry the following substituents:hydroxyl, phenyl, 1,3-dioxan-2-yl, 1,3-dioxolan-2-yl, --NHR⁵, --NHCOR⁵,--CONHR⁵, --OCONHR⁵, --N.sup.⊕ (R⁵)₃.An.sup.Θ, --SO₃ H or --SO₃.sup.ΘKa¹⁰⁸, where

R⁵ is one of the unsubstituted or hydroxyl- or phenyl-substituted alkylradicals R⁴ or phenyl and the radicals R⁵ in the substituent --N.sup.⊕(R⁵)₃ may be identical or different,

An.sup.⊖ is the equivalent of an anion, and

Ka.sup.⊕ is the equivalent of a cation,

R² and R³ are identical or different C₁ -C₁₀ -alkyl groups or togetherone of the radicals R¹, provided that in the case of the group A1radicals R¹ of the formulae ##STR5## in which X is oxygen, sulfur,selenium, --N(CH₃)₂ or ##STR6## and which may be substituted by alkyl,aryl or amino groups shall be excluded and in the case of the group A2radicals R¹ of the formulae ##STR7## in which Y is oxygen or sulfurshall be excluded, m and n are=identical or different integers from 0 to3.

Dyes which absorb in the infrared region are of interest for manyapplications. They are frequently used as sensitizers forelectrophotographic layers and for photopolymerizations and as laserlight sensitive dyes in optical recording media.

If the dyes are additionally suitable for generating singlet oxygen,they are also of interest for use in photodynamic tumor therapy, whichis based on the selective accumulation of dyes in cancer tissue andmakes possible not only precise localization but also effectivetreatment even at an early stage of the tumor.

The irradiation of dye-enriched tumor tissue leads, probably viaformation of singlet oxygen, to the selective destruction of the tumortissue. Since the light transmissivity of body tissue rises steeply withincreasing wavelength and for IR radiation of 800 nm is several powersof ten greater than for visible light, semiconductor lasers which emitlight in the near IR region and dyes which show high absorption in thatregion are particularly suitable radiation sources for tumor therapy.

U.S. Pat. No. 5,002,812 and JP-A-242 288 (1989) describe the use ofmethine dyes having a cyclopentanetrione group based on benzofusedindoline or on 3-ethylbenzothiazole and pyridine-, pyran- andthio-pyrans in optical recording media.

U.S. Pat. No. 3,140,951 discloses methine dyes with a cyclohexanetetronegroup based on 3-ethyl-benzoxazole and -benzothiazole,1-ethyl-3,3-dimethyl-2-indole and 1-ethyl-2(1H)- and -4(1H)-quinoline,which, however, are used there as desensitizers for photographicemulsions.

It is an object of the present invention to find dyes which absorb inthe infrared region and have favorable application properties.

We have found that this object is achieved by the polyketomethine dyesI.

The radical R¹ is a 5- or 6-membered cycloaliphatic radical whichcontains one or two hetero atoms from the group --NR⁴ --, --O-- and--S-- and which can be fused linearly or angularly with an isoaromaticor heteroaromatic group. Examples of preferred radicals R¹ are: ##STR8##

Examples of particularly preferred radicals R¹ are: ##STR9##

A very particularly preferred radical R¹ is ##STR10##

The fused benzene and naphthalene nuclei are preferably unsubstituted.However, they may also carry C₁ -C₅ -alkyl, -alkoxy, halogen, --SO₃ H or--SO₃.sup.⊖ Ka.sup.⊕ as substituents.

Suitable for use as radical R⁴ are C₁ -C₂₀ -alkyl groups such as methyl,ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl,heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl andeicosyl and also branched radicals of this kind. Of these, the C₁ -C₁₂-alkyl groups are preferred and the C₁ -C₆ -alkyl groups particularlypreferred.

The carbon chains of these alkyl groups may be interrupted by oxygenatoms in ether function. In this case the C₁ -C₆ -alkyl groups generallycontain one or two oxygen atoms in the chain, the C₇ -C₁₂ -alkyl groupsup to three and the C₁₃ -C₂₀ -alkyl groups up to five. Examples are thefollowing groups: preferably 2-methoxy-, 2-ethoxy-, 2-propoxy-,2-isopropoxy- and 2-butoxyethyl, plus 2- and 3-methoxypropyl, 2- and3-ethoxypropyl, 2- and 4-ethoxy-butyl, 2- and 4-isopropoxybutyl,5-ethoxypentyl, 6-methoxyhexyl, 4-oxa-6-ethyldecyl, preferably3,6-dioxaheptyl, 3,6-dioxaoctyl, 3,6-dioxadecyl, 3,6,9-trioxadecyl and3,6,9-trioxaundecyl.

The alkyl radicals R⁴ may additionally carry substituents such ashydroxyl, phenyl, 1,3-dioxan-2-yl and 1,3-dioxolan-2-yl. Examples are(Ph=phenyl):

--(CH₂)₂ --OH, --(CH₂)₃ --OH, --CH₂ --CH(OH)--CH₃, --(CH₂)₄ --OH, --CH₂--CH(OH)--CH₂ --CH₃, --(CH₂)₅ --OH, --(CH₂)₆ --OH, --(CH₂)₇ --OH,--(CH₂)₈ --OH und --(CH₂)₁₁ --OH; --CH₂ --Ph, --(CH₂)₂ --Ph,--CH(Ph)--CH₃ und --[(CH₂)₂ --O]₂ --CH₂ --Ph; ##STR11##

Further possible substituents for the alkyl radicals R⁴ are those of theformulae --NH--R⁵, --NH--CO--R⁵, --CO--NH--R⁵ and --O--CO--NH--R⁵, whichare preferably in the ω-position. Here R⁵ is one of the unsubstituted orhydroxyl- or phenyl-substituted alkyl radicals R⁴ whose carbon chain maybe interrupted by oxygen atoms in ether function or phenyl. Examples ofthe radical R⁵ are the appropriate groups listed above. Such substitutedradicals R⁴ are for example:

--(CH₂)₂ --NH--CH₃, --(CH₂)₃ --NH--C₂ H₅, --CH(CH₃)--CH(CH₃)--NH--C₂ H₅,--(CH₂)₄ --NH--C₃ H₇, --(CH₂)₃ --NH--CH(CH₃)₂, --(CH₂)₂ --NH--C₄ H₉ and--(CH₂)₂ --NH--Ph;

--CH(CH₃)--CH(CH₃)--NH--CO--CH₃, --(CH₂)₄ --NH--CO--C₂ H₅, --(CH₂)₃--NH--CO--C₃ H₇, --(CH₂)₂ --NH--CO--CH(CH₃)₂, --(CH₂)₂ --NH--CO--C₄ H₉,--(CH₂)₂ --CO--NH--C(CH₃)₃ and --(CH₂)₂ --NH--CO--Ph;

--CH(CH₃)--CH(CH₃)--CO--NH--CH₃, --(CH₂)₄ --CO--NH--C₂ H₅, --(CH₂)₃--CO--NH--C₃ H₇, --(CH₂)₂ --CO--NH--CH(CH₃)₂, --(CH₂)₂ --CO--NH--C₄ H₉,--(CH₂)₂ --CO--NH--C(CH₃)₃ and --(CH₂)₂ --CO--NH--Ph;

--(CH₂)₄ --O--CO--NH--CH₃, --(CH₂)₃ --O--CO--NH--C₂ H₅, --(CH₂)₃--O--CO--NH--C₃ H₇, --(CH₂)₃ --O--CO--NH--CH(CH₃)₂, --(CH₂)₃--O--CO--NH--C₄ H₉, --(CH₂)₃ --O--CO--NH--C(CH₃)₃ and --(CH₂)₂--O--CO--NH--Ph.

Finally, substituents for the alkyl radicals R⁴ may also be those of theformulae --N.sup.⊕ (R⁵)₃.An.sup.⊖, --SO₃ H or --SO₃.sup.⊖.Ka.sup.⊕,likewise preferably in the ω-position. These radicals R⁵ can beidentical or different. Examples of these radicals R⁴ are:

--(CH₂)₂ --N.sup.⊕ (C₂ H₅)₃, --(CH₂)₃ --N.sup.⊕ (CH₃)₃, --(CH₂)₃--N.sup.⊕ (C₂ H₅)₃, --(CH₂)₃ --N.sup.⊕ (C₄ H₉)₃, --(CH₂)₄ --N.sup.⊕ (C₂H₅)₃, --(CH₂)₆ --N.sup.⊕ (C₂ H₅)₃, --(CH₂)₁₀ --N.sup.⊕ (C₂ H₅)₃,--(CH₂)₂ --N.sup.⊕ (CH₃) (C₂ H₅)₂ und --(CH₂)₂ N.sup.⊕ (CH₃)(C₂ H₅)(C₃H₇);

--(CH₂)₂ --SO₃ H, --(CH₂)₃ --SO₃ H, --(CH₂)₄ --SO₃ H, --(CH₂)₄ --SO₃ H,--(CH₂)₆ --SO₃ H and --(CH₂)₁₀ --SO₃ H;

--(CH₂)₂ --SO₃.sup.⊖, --(CH₂)₃ --SO₃.sup.⊖, --(CH₂)₄ --SO₃.sup.⊖,--(CH₂)₆ --SO₃.sup.⊖ and --(CH₂)₁₀ --SO₃.sup.⊖.

Suitable anions An.sup.⊖ can be anions of inorganic or organic acids.Particular preference is given for example to chloride, bromide andsulfate and also maleate, fumarate, tosylate and salicylate.

Suitable cations Ka.sup.⊕ can be alkali metal ions such as in particularNa.sup.⊕ and K.sup.⊕. Particular preference is given to trialkylammoniumions of the formula HN.sup.⊕ (R⁵)₃, for example those with theabovementioned groups --N.sup.⊕ (R⁵)₃.

Also suitable for use as radical R⁴ are cyclopentyl, cyclohexyl,cycloheptyl and phenyl which may carry halogen, C₁ -C₄ -alkyl or -alkoxyas substituents, such as: 2-, 3- and 4-chlorophenyl, 2,4- and2,6-dichlorophenyl, 2-, 3- and 4-bromophenyl, 2-, 3- and 4-methylphenyl,2,4-dimethylphenyl, 2-, 3- and 4-methoxyphenyl and 2,4-dimethoxyphenyl.

Suitable for use as radicals R² and R³ are the alkyl groups with up to10 carbon atoms listed for the radical R⁴ in which case R² and R³ arepreferably identical alkyl groups and are each particularly preferablymethyl.

However, the radicals R² and R³ may also be together one of theabovementioned radicals R¹. In this case not only asymmetrically butalso symmetrically constructed methine dyes are possible, the latterbeing preferred.

The variables m and n are identical or different and can be 0, 1, 2 or3. m is preferably 0 and particularly preferably 1. If the radicals R²and R³ are each alkyl groups, n is preferably 0. If the radicals R² andR³ together form a radical R¹, n preferably has the same value as m.

Methods for preparing methine dyes with a cyclohexanetetrone group aregenerally known; see for example US-A-3 140 951.

The polyketomethine dyes I according to the invention can be prepared ina similar manner, for example by condensing the group A compounds1,2,4-cyclopentanetrione or 2,5-dihydroxy-p-benzoquinone with the##STR12## heterocyclic ammonium salts of the formula IIa ##STR13## whereX is a leaving group, which are described for example in Houben-Weyl,4th edition, Volume V/1d, pages 239 to 240 (1972) or in J. HeterocyclicChem. 22 (1985), 1727-1734.

If m is 0, X is preferably a methylmercapto group, while if m≧1 thepreferred leaving group is acetanilido.

A further way of introducing the group ##STR14## is to use thecorresponding aldehydes of the formula IIb ##STR15## in thecondensation.

The compounds IIa and IIb are obtainable by reacting the respectiveunsubstituted nitrogen heterocycles with a compound R⁴ -Y where Y is forexample chlorine, bromine, iodine, --O--SO₂ --Ph--4--CH₃, --O--SO₂ --CH₃or --O--SO₂ --CF₃.

If m is 0 it is also possible to use the activated dimeric heterocycles,for example those of the formulae ##STR16##

Vice versa, the condensation can also be carried out similarly to US-A-3140 951 or Houben-Weyl, 4th edition, Volume V/1d, pages 239 to 290(1972), with 1,2,4-cyclopentanetrione or 1,2,4,5-cyclohexanetetronewhich is in each case disubstituted by anilinomthylene (leaving group--NH--Ph), and the 2-methylated heterocyclic ammonium salts (m=1).

To form the polymethine chain (m=2 or 3) the 2-methylated heterocyclicsalts can be reacted, for example as described in Houben-Weyl, 4thedition., Volume V/1d, pages 268 to 274 (1972), with, for example,compounds of the formula ##STR17## in acetic anhydride to form ahemicyanine of the formula ##STR18## which can then be used for furthercondensation with group A.

To prepare the similarly novel asymmetrical polyketomethine dyes of theformula I where R² and R³ are each alkyl, the starting materials usedfor the condensation are 5,5- and 6,6-dialkylated1,2,4-cyclopentanetriones and 2,5-dihydroxy-p-benzoquinonesrespectively.

The condensation is preferably carried out in a solvent, such as diethylether, tetrahydrofuran, trichloroethylene, 1,1,1-trichloroethane,methylene chloride, chloroform, methanol, ethanol, propanol,isopropanol, butanol, glacial acetic acid, propionic acid oracetonitrile, preferably in the presence of a catalyst, such as ammoniumacetate, piperidine or pyridine or acetates thereof, at a temperaturebetween 20° C. and the boiling point of the solvent used.

Preference is given to using tertiary amines such as tripropylamine,tributylamine and in particular triethylamine, picolines, lutidines andin particular pyridine or mixtures thereof as solvents, since in thesecases no separate catalyst need be added.

A further way of preparing methine dyes I with dialkylation in the6-position of the cyclohexanetetrone consists in reacting the5,5-dialkyl-1,3-cyclohexanedione with a heterocyclic ammonium salthaving a leaving group and then selectively oxidizing the resultingcondensation product with selenium dioxide in a solvent such as glacialacetic acid to give the corresponding tetraketo compound.

The polyketomethine dyes I of the invention show in some cases highabsorption in the infrared region. They are highly suitable forproducing singlet oxygen and can therefore be used in photodynamic tumortherapy, for example.

They are also suitable for use as sensitizers in electrophotographicrecording materials as are described for example in EP-A-150 419.Suitable monolayered systems of this type preferably support on aconductive base material a layer comprising from 45 to 75 parts byweight of a binder, from 30 to 60 parts by weight of a charge carriertransporter compound, optionally up to 25 parts by weight of a further,essentially inactive binder and from 0.05 to 0.8 part by weight of thesensitizer which generates charge carriers on actinic irradiation. Thislayer is advantageously applied to the purified conductive base materialfrom an approximately 6% strength by weight solution in a suitableorganic solvent in such as way as to leave, after the solvent has beenflashed off, a dry layer in a thickness, depending on the intended use,from about 0.8 to 40 μm, especially in the case of electrophotographicprinting plates from 0.8 to 6 μm. Further details on the formation ofthese systems can be found in EP-A-150 419.

Furthermore, the dyes I are suitable for use as sensitizers forphotopolymerizations, for example for the curing of surface coatings.Finally, they can be used, as described in US-A-4 904 566 for azulenesquaric acid dyes, as laser light sensitive dyes in optical recordingmedia.

EXAMPLES

a) Preparation of polyketomethine dyes I

a1) Preparation of symmetrical triketomethine dyes Ia' ##STR19##

Example 1 ##STR20##

A mixture of 1.61 g (5 mmol) of 3-methyl-2-methylmercaptobenzothiazoliumiodide, 0.28 g (2.5 mmol) of 1,2,4-cyclopentanetrione and 2 ml offreshly distilled triethylamine in 20 ml of ethanol was refluxed for 30min.

The precipitate produced on quenching was separated off, washed insuccession with methanol, ethyl acetate and ether and thenrecrystallized twice from dimethylformamide.

The 3,5-di-(3-methyl-2-benzothiazolinylidene )-1,2,4-cyclopentanetrionewas obtained in a yield of 0.45 g (42% of theory):

melting point:>250° C.; λ_(max) =467 nm (CH₂ Cl₂).

Example 2 ##STR21##

The reaction with 1.37 g (5 mmol) of3-methyl-2-methylmercaptothiazolinium iodide was carried out asdescribed in Example 1. The product was recrystallized fromacetonitrile.

The 3,5-di-(3-methyl-2-thiazolinylidene)-1,2,4-cyclopentanetrione wasobtained in a yield of 0.35 g (45% of theory):

melting point:>250° C.; λ_(max) =399 nm (CH₂ Cl₂).

Example 3 ##STR22##

A mixture of 1.31 g (5 mmol) of 2-methylmercapto-1,3-dithiolaniummethosulfate, 0.28 g (2.5 mmol) of 1,2,4-cyclopentanetrione and 2 ml offreshly distilled triethylamine in 20 ml of pyridine was refluxed for 45min.

The precipitate produced on cooling was separated off, washed insuccession with methanol and ethyl acetate and recrystallized fromdimethylformamide.

The 3,5-di(2-dithiolanylidene)-l,2,4-cyclopentanetrione was obtained ina yield of 0.48 g (61% of theory):

melting point:>250° C.; λ_(max) =446 nm (dimethylformamide).

Examples 4 TO 7

The triketomethine dyes Ia' shown in Table 1 were prepared analogouslyto Example 3 by reacting 1,2,4-cyclopentanetrione with2-methylmercapto-l,3-dithiolium methosulfate (Example 4) or with thecorresponding heterocyclic ammonium iodide with an acetanilidovinylsubstituent in the 2-position (Examples 5 to 7).

                  TABLE 1                                                         ______________________________________                                         ##STR23##                     Ia'                                                                      Yield in                                                                             mp.   λ.sub.max                       Ex.  R.sup.1        m     g/%    [°C.]                                                                        [nm]                                   ______________________________________                                              ##STR24##     0      0,62/79*                                                                            >250  527 (CH.sub.2 Cl.sub.2)                5                                                                                   ##STR25##     1     0,84/86                                                                              >250  597 (dimethyl- formamide)              6                                                                                   ##STR26##     1     0,93/76                                                                              >250  678 (dimethyl- formamide)              7                                                                                   ##STR27##     1     0,82/72                                                                              >250  618 (dimethyl- formamide)              ______________________________________                                         *Recrystallized from N,Ndimethylacetamide                                

Example 8 ##STR28##

A mixture of 1.52 g (5mmol) of 1-ethyl-4-methylquinolinium iodide, 0.80g (2.5 mmol) of 3,5-dianilinomethylene-1,2,4-cyclopentanetrione and 1 mlof freshly distilled triethylamine in 20 ml of acetonitrile was stirredin the dark at room temperature for 3 days.

The resulting precipitate was separated off, washed with methanol andrecrystallized from N,N-dimethylformamide.

The 3,5-di((1-ethyl-4(1H)quinolinylidene)-ethylidene)-1,2,4-cyclopentanetrione was obtained in a yield of 0.68 g(57% of theory):

melting point:>250° C.; λ_(max) =816 nm (dimethyl sulfoxide).

Examples 9 TO 13

The triketomethine dyes Ia" listed in Table 2 were prepared analogouslyto Example 8 by reacting 3,5-dianilinomethylene-1,2,4-cyclopentanetrionewith the corresponding heterocyclic ammonium iodide and obtained insimilar yields.

                  TABLE 2                                                         ______________________________________                                         ##STR29##                    Ia"                                             Ex.  R.sup.1             λ.sub.max  [nm]                               ______________________________________                                         9                                                                                  ##STR30##          731 (dimethyl sulfoxide)                             10                                                                                  ##STR31##          662 (dimethyl sulfoxide)                             11                                                                                  ##STR32##          652 (CH.sub.2 Cl.sub.2)                              12                                                                                  ##STR33##          655 (CH.sub.2 Cl.sub.2)                              13                                                                                  ##STR34##          621 (dimethyl sulfoxide)                             ______________________________________                                    

Example 14 ##STR35##

A mixture of 1.46 g (5 mmol) of1,3-dimethyl-2-methylmercaptobenzimidazolium perchlorate, 0.28 g (2.5mmol) of 1,2,4-cyclopentanetrione and 2 ml of freshly distilledtriethylamine in 20 ml of acetonitrile was refluxed for 2h.

The precipitate formed on cooling was separated off, washed with waterand recrystallized from N,N-dimethylacetamide.

The 3,5-bis(1,3-dimethyl-2-benzimidazolinylidene)-1,2,4-cyclopentanetrione wasobtained in a yield of 0.23 g (23% of theory):

melting point:>250° C.; λ_(max) =362 nm (CH₂ Cl₂).

Example 15 ##STR36##

A solution of 1.40 g (2 mmol) of 9,9'-oxybis(10-methylacridinium) bis(trifluoromethanesulfonate ) in 20 ml of acetonitrile was added dropwiseat room temperature to a mixture of 0.11 g (1 mmol) of1,2,4-cyclopentanetrione, 20 ml of acetonitrile and 2 ml of freshlydistilled triethylamine.

The resulting precipitate was separated off and washed with a largeamount of methylene chloride.

The 3,5-bis(10-methyl-9-acridanylidene)-1,2,4-cyclopentanetrione wasobtained in a yield of 0.42 g (71% of theory):

melting point:>250° C.; λ_(max) =788 nm (CH₂ Cl₂).

a2) Preparation of symmetrical tetraketomethine dyes Ib' ##STR37##

Example 16 ##STR38##

A mixture of 4 g (14.5 mmol ) of 3-methyl-2-methylmercaptothiazoliniumiodide, 1 g (7.1 mol ) of 2,5-dihydroxy-p-benzoquinone and 2.5 ml offreshly distilled triethylamine in 40 ml of pyridine was refluxed for 10min.

The precipitate formed on cooling was separated off and recrystallizedfrom dimethylformamide.

The 3,6-di- (3-methyl-2-thiazolinylidene ) -1,2,4,5-cyclohexanetetronewas obtained in a yield of 1.09 g (45% of theory):

melting point:>300° C.; λ_(max) =372 nm (dimethyl sulfoxide).

Example 17 ##STR39##

A mixture of 2.62 g (10 mmol) of 2-methylmercapto-1,3-dithiolaniummethosulfate, 0.70 g (5mmol) of 2,5-dihydroxy-p-benzoquinone and 2 ml offreshly distilled triethylamine in 30 ml of pyridine was refluxed for 15min.

The precipitate formed on quenching was separated off, washed insuccession with methanol and acetone and then dissolved in hot m-cresol.After filtration, the still hot solution was poured into an excess ofcold methanol to precipitate the target product.

The 3,6-bis(1,3-dithiolan-2-ylidene)-1,2,4,5-cyclohexanetetrone wasobtained in a yield of 1.02 g (59% of theory):

melting point:>300° C.; λ_(max) =415 nm (dimethyl sulfoxide).

Example 18 ##STR40##

The reaction with 2.60 g (10 mmol) of 2-methyl-mercapto-1,3-dithioliummethosulfate and the isolation of the product were each carried outanalogously to Example 17.

The 3,6-bis (1,3-dithiol-2-ylidene)-1,2,4,5-cyclohexanetetrone wasobtained in a yield of 1.46 g (86% of theory):

melting point: 300° C.; λ_(max) =466 nm (dimethyl sulfoxide).

Example 19 ##STR41##

A mixture of 2.88 g (10 mmol) of 1,2,3-trimethyl-benzimidazolium iodideand 0.69 g (2 mmol ) of3,6-dianilinomethylene-1,2,4,5-cyclohexanetetrone in 25 ml ofN,N-dimethylformamide was refluxed for 2 min.

The precipitate formed on quenching was separated off, repeatedly washedwith methanol and recrystallized from N,N-dimethylacetamide.

The 3,6-bis (2-(1,3-dimethyl-2-benzimidazolinylidene)ethylidene)-1,2,4,5-cyclohexanetetrone was obtained in a yield of 0.43 g (45% oftheory):

melting point:>280° C.; λ_(max) =477 nm (CH₂ Cl₂).

Example 20 ##STR42##

A solution of 1.40 g (5 mmol) of 9,9'-oxybis(10-methylacridinium)bis(trifluoromethanesulfonate) in 20 ml of acetonitrile was addeddropwise at room temperature to a mixture of 0.14 g (1 mmol) of2,5-dihydroxy-p-benzoquinone, 20 ml of acetonitrile and 2 ml of freshlydistilled triethylamine.

The precipitate formed was separated off and washed with a large amountof methylene chloride.

The 3,6-bis(10-methyl-9-acridanylidene)-1,2,4,5-cyclohexanetetrone wasobtained in a yield of 0.38 g (61% of theory):

melting point:>250° C.; λ_(max) =693 nm (CH₂ Cl₂).

Example 21 ##STR43##

A mixture of 2.28 g (8.6 mmol) of 2-ethyl-1-methylbenzo[c,d]indoliumiodide, 1.00 g (2.9 mmol) of3,6-dianilinomethylene-1,2,4,5-cyclohexanetetrone and 1 ml of freshlydistilled triethylamine in 30 ml of pyridine was refluxed for 10 min.

The precipitate formed on quenching was separated off, washed insuccession with methanol and diethyl ether and then dried.

The3,6-di((2-ethylbenzo[c,d]indolinylidene)-ethylidene)-1,2,4,5-cyclohexanetetronewere obtained in a yield of 1.4 g:

λ_(max) =751 nm (CH₂ Cl₂).

Examples 22 TO 28

The tetraketomethine dyes Ib" listed in Table 3 were preparedanalogously to Example 21 by reacting3,6-dianilinomethylene-1,2,4,5-cyclohexanetetrone with the correspondingheterocyclic ammonium iodide.

                  TABLE 3                                                         ______________________________________                                         ##STR44##                    Ib"                                             Ex.   R.sup.1               λ.sub.max  [nm]                            ______________________________________                                        22                                                                                   ##STR45##            725 (CH.sub.2 Cl.sub.2)                           23                                                                                   ##STR46##            723 (CH.sub.2 Cl.sub.2)                           24                                                                                   ##STR47##            732 (CH.sub.2 Cl.sub.2)                           25                                                                                   ##STR48##            731 (CH.sub.2 Cl.sub.2)                           26                                                                                   ##STR49##            623 (CH.sub.2 Cl.sub.2)                           27                                                                                   ##STR50##            603 (CH.sub.2 Cl.sub.2)                           28                                                                                   ##STR51##            611 (CH.sub.2 Cl.sub.2)                           29                                                                                   ##STR52##            634 (dimethyl- formamide)                         ______________________________________                                    

Example 30 ##STR53##

A mixture of 1.92 g (6.5 mmol ) of2,3,3-trimethylindolinium-1-(butane-4-sulfonate), 1.00 g (2.9 mmol ) ofdianilinomethylene-1,2,4,5-cyclohexanetetrone and 2 ml of freshlydistilled triethylamine in 30 ml of pyridine was refluxed for 10 min.

After cooling, the precipitate formed was separated off, washed withethyl acetate and dried.

Yield: 0.25 g; melting point: 265° C.

a3) Preparation of asymmetrical tetraketomethine dyes Ic ##STR54##

Example 31 ##STR55##

A mixture of 0.32 g (1 mmol) of 1-ethyl-2,3,3-trimethylindoliniumiodide, 0.27 g (1 mmol.) of 3-anilinomethylene-6,6-dimethyl-1,2,4,5-cyclohexanetetrone and 0.5 ml of freshly distilled triethylaminein 10-15 ml of acetonitrile was stirred at an oil bath temperature of50° C. for 3 days.

The precipitate formed was separated off, washed with water, dried, andrecrystallized from dioxane.

The6,6-dimethyl-3-(2-(1-ethyl-3,3-dimethyl-2-indolinylidene)ethylidene)-1,2,4,5-cyclohexanetetronewere obtained in a yield of 0.19 g (52% of theory):

melting point:>250° C.; λ_(max) =507 nm (CH₂ Cl₂).

Examples 32 TO 36

The tetraketomethine dyes Ic listed in Table 4 were prepared analogouslyto Example 31 by reacting3-anilinomethylene-6,6-dimethyl-1,2,4,5-cyclohexanetetrone with thecorresponding heterocyclic ammonium iodide.

                  TABLE 4                                                         ______________________________________                                         ##STR56##                     Ic                                                                 Yield in  mp.   λ.sub.max                          Ex.  R.sup.1        g/%       [°C.]                                                                        [nm]                                      ______________________________________                                        32                                                                                  ##STR57##     0,23/66   >250  504 (dimethyl- formamide)                 33                                                                                  ##STR58##     0,23/81   >250  483 (CH.sub.2 Cl.sub.2)                   34                                                                                  ##STR59##      0,09/29* >250  443 (dimethyl- formamide)                 35                                                                                  ##STR60##      0,31/89**                                                                              >250  520 (Cl.sub.2 Cl.sub.2)                   36                                                                                  ##STR61##      0,33/95**                                                                              >250  539 (CH.sub.2 Cl.sub.2)                   ______________________________________                                         *Recrystallized from ethanol                                                  **Recrystallized from N,Ndimethylformamide                               

Example 37 ##STR62##

A mixture of 8.62 g (0.03 mmol) of5,5-dimethyl-2-(3-methylbenzothiazolinylidene)-1,3-cyclohexanedione,obtained by 1:1 condensation of 5,5-dimethyl-1,3-cyclohexanedione with3-methyl-2-methylmercaptobenzothiazolium iodide in boiling 2-propanol,and 7.77 g (0.07 mol) of selenium dioxide in 50 ml of glacial aceticacid was stirred at an oil bath temperature of 130° C. for 5 h.

The resulting elemental selenium was separated off, and the glacialacetic acid was removed in a rotary evaporator. The residue was taken upin methylene chloride and filtered at the boil to remove insolubles. Theremaining solution was cooled down to -15° C. to bring down crystals ofthe target product.

The6,6-dimethyl-3-(3-methylbenzothiazolinylidene)-1,2,4,5-cyclohexanetetronewas obtained in a yield of 4.42 g (47% of theory):

melting point:>250° C.; λ_(max) =389 nm (dimethyl sulfoxide).

b) Use Examples

b1) Production of singlet oxygen

The dyes I listed in Tables 5 and 6 and prepared analogously to a) weredissolved in the stated solvent and stimulated with a dye laser in theabsorption bands.

The singlet oxygen formed was determined by time-resolved measurement ofthe phosphorescence at 1270 nm using a germanium diode cooled withliquid nitrogen (for the method see J. Amer. Chem. Soc. 111 (1989),2909-2914); the calibrating substance used was 1,5-diaminoanthraquinone.

                  TABLE 5                                                         ______________________________________                                         ##STR63##                                                                                              Singlet oxygen                                                                          λ                                  Ex.  R.sup.1        m     yield [%] [nm]                                      ______________________________________                                        1A                                                                                  ##STR64##     0     20,1      446 (dimethyl- formamide)                 2A                                                                                  ##STR65##     1      1,1      670 (methanol)                            ______________________________________                                    

                                      TABLE 6                                     __________________________________________________________________________     ##STR66##                                                                                                    Singlet oxygen                                                                        λ                              Ex.                                                                              R.sup.1           R.sup.1'   yield [%]                                                                             [nm]                                  __________________________________________________________________________    3A                                                                                ##STR67##        R.sup.1    8,3     590 (CH.sub.2 Cl.sub.2)               4A                                                                                ##STR68##        R.sup.1    4,7     590 (ethanol)                         5A                                                                                ##STR69##        R.sup.1    4,4     634 (dimethylformamide)               6A                                                                                ##STR70##                                                                                       ##STR71## 1,9     462 (dimethylformamide)               7A                                                                                ##STR72##        R.sup.1    2,6     670 (CH.sub.2 Cl.sub.2)               8A                                                                                ##STR73##        R.sup.1    6,1     670 (CH.sub.2 Cl.sub.2)               9A                                                                                ##STR74##        R.sup.1    9,8     600 (toluene)                         __________________________________________________________________________

b2) Preparation of photoconductor layers

The dyes I listed in Table 7 and prepared analogously to a) were usedfor preparing photoconductor layers.

To this end a 10% strength by weight solution of a mixture of 1% byweight of dye I as sensitizer, 27% by weight of2-(4'-ethylphenylaminophenyl)-6-methoxybenzo-1,2,3-triazole and 18% byweight of 2,5-bis-4,4-diethylaminophenyl-1,2,3-oxadiazole as chargecarrier transporter compounds and 54% by weight of a copolymer of 55% byweight of styrene, 25% by weight of acrylic acid, 15% by weight ofmaleic anhydride and 5% by weight of vinyl acetate (K value 36) asbinder was stirred in 1:1 acetone/tetrahydrofuran at room temperaturefor 3 h.

After filtration, the solution was applied with a doctor blade to afinely brushed, 105 μm thick sheet of aluminum in such a way as toproduce, after solvent flashoff and drying (15 min at 80° C.), a coatingwith a dry film thickness of 4.0±0.1 μm.

The plate thus coated was stored in the dark for 25 h and charged upwith a high-voltage corona to the surface potential maximum. Then theloss of potential in the course of 20 sec in the dark (darkconductivity) and the photopotential decay induced by irradiation withthe white light of a 100 W XDO xenon high-pressure lamp at a distance of45 cm in the course of 10 sec were measured.

                                      TABLE 7                                     __________________________________________________________________________     ##STR75##                                                                                          Potential loss                                                                        Photopotential decay                            Ex.                                                                              R.sup.1            in the dark [%]                                                                       [%]                                             __________________________________________________________________________    10A                                                                               ##STR76##         32,0    95,7                                            11A                                                                               ##STR77##         21,9    73,8                                            12A                                                                               ##STR78##         13,4    81,1                                            __________________________________________________________________________

We claim:
 1. Polyketomethine dyes of the formula I ##STR79## where A isa group of the formula A1 or A2 ##STR80## R¹ is 5- or 6-memberedcycloaliphatic radical which contains one or two heteroatoms from thegroup --O-- and --S-- and which may be fused to an isoaromatic group,R²and R³ are identical or different C₁ -C₁₀ -alkyl groups or together oneof the radicals R¹, provided that in the case of the group A1 radicalsR1 of the formula ##STR81## in which X is oxygen, sulfur, selenium,--N(CH₃)₂ or --N(C₂ H₅)--CH₂ and which may be substituted by alkyl, arylor amino groups shall be excluded; and m and n are identical ordifferent integers from 0 to 3.